Effects of Air Velocity On Muskmelon Plant Growth, Yield and Fruit Quality in Chinese Solar Greenhouse

The effect of different air velocities (0.4 m·s^-1, 1.0 m·s^-1 and 2.2 m·s^-1) on muskmelon (Cucumis melo) in a single span, lean-to greenhouse (or ‘solar greenhouse’) was analyzed. The air velocity treatment was applied using a polytube air guide attached to a mechanical fan from 8 am (after rolling up heat insulating covering of the roof) to 11:30 am and from 3 pm to 5 pm every day after fruit setting. No air velocity treatment was applied from 11:30 am to 3 pm, during which the greenhouse was well ventilated for cooling. After 40 days of air velocity treatment, the plant growth, yield and the quality of fruit were significantly affected by air velocity. The results showed that the treatment of 1.0 m·s^-1 air velocity achieved the greatest increase in plant growth and yield among the three air velocity treatments: 21.7% more single leaf area, 63.1% more LAI, 120.3% higher stomatal conductance, 2 days earlier maturation, 24.4% more fruit yield, and 11.1% higher total sugar in fruit, respectively, than those in the control (without wind treatment). The total soluble solids of fruit at 0.4 m·s^-1, 1.0 m·s^-1 and 2.2 m·s^-1 air velocity were 5.8%, 12.6% and 13.9%, respectively greater than those in the control. The protein concentrations of fruit at 0.4 m·s^-1, 1.0 m·s^-1 and 2.2 m·s^-1 increased by 2.9%, 2.7% and 3.6%, respectively, compared to those in the control. The reduced sugar concentrations of fruit at 0.4 m·s^-1,1.0 m·s^-1 and 2.2 m·s^-1 decreased by 3.2%,7.2% and 9.7% comparing to those in the control, respectively. Fruit pulp thickness and vitamin C showed no significant effects by air velocity. In conclusion, the effect of different air velocity on muskmelon in the single span, lean-to greenhouse was significant and the optimal air velocity was 1.0 m·s^-1.